Pin tumbler lock and key structure

ABSTRACT

A pin tumbler lock having a cylindrical lock housing receiving a rotatable plug shaft with a front barrel and a rear barrel secured thereon, a center barrel secured in the lock housing and an index ring stationarily mounted in the lock housing and encompassing the front barrel. The front, center and rear barrels have a plurality of axially extending passages receiving tumblers, change tumblers and locking pins. The index ring includes a pair of oppositely disposed radial openings normally aligned with radial openings in the front barrel and receiving a pair of inwardly biased retaining pins having rounded inner ends cooperating with depressions in the surface of the key. Rearwardly of the retaining pins is a second pair of radial openings in the index ring normally aligned with radial openings in the front barrel to receive inwardly biased drivers and antitorque pins also cooperating with the exterior surface of the key. The plug shaft within the front barrel is provided with a plurality of circumferentially equally spaced longitudinal ribs which cooperate with longitudinal grooves on the interior surface of the key so that rotation of the key provides simultaneous rotation of the plug shaft as well as the front and rear barrels and a lock bolt on the rear end of the shaft if the retaining pins, antitorque tumblers and axial pin tumblers are properly oriented by the key.

llnite States Patent Walters et al.

[ Mar. 14, 11972 [54] UN TUMBLER LOCK AND KEY STRUCTURE [72] inventors: Russell W. Walters; Richard M. Brattland,

both of Rockford, 111.

Keystone Consolidated Industries, Inc., Peoria, 111.

[22] Filed: Mar. 27, 1970 [21] Appl.No.: 23,389

[73] Assignee:

Primary Examiner-Robert L. Wolfe Attomey-Wilson & Geppert [57] ABSTRACT A pin tumbler lock having a cylindrical lock housing receiving a rotatable plug shaft with a front barrel and a rear barrel secured thereon, a center barrel secured in the lock housing and an index ring stationarily mounted in the lock housing and encompassing the front barrel. The front, center and rear barrels have a plurality of axially extending passages receiving tumblers, change tumblers and locking pins. The index ring includes a pair of oppositely disposed radial openings normally aligned with radial openings in the front barrel and receiving a pair of inwardly biased retaining pins having rounded inner ends cooperating with depressions in the surface of the key Rearwardly of the retaining pins is a second pair of radial openings in the index ring normally aligned with radial openings in the front barrel to receive inwardly biased drivers andantitorque pins also cooperating with the exterior surface of the key. The plug shaft within the front barrel is provided with a plurality of circumferentially equally spaced longitudinal ribs which cooperate with longitudinal grooves on the interior surface of the key so that rotation of the key provides simultaneous rotation of the plug shaft as well as the front and rear barrels and a lock bolt on the rear end of the shaft if the retaining pins, antitorque tumblers and axial pin tumblers are properly oriented by the key.

Paten "-11 March 14, $19111??? 3 Sheets-Sheet 1 PIN TIJMBLER LOCK AND KEY STRUCTURE The present invention relates to a pin tumbler lock and key construction and more particularly to improvements in an axial pin tumbler lock.

In the recent Monahan US. Pat. No. 3,422,646, entitled Instantaneous Tumbler Change Lock," is disclosed a lock structure having axially movable pin tumblers which are actuated by a hollow cylindrically shaped key where the lock structure included a plurality of tumblers, a plurality of change tumblers or wafers, and locking pins corresponding to the number of tumblers. The change tumblers or wafers provide for easily changing the lock setting to be actuated by a differently bitted key through the use of a change key and change position of the lock. The present invention relates to improvements in pin tumbler locks, especially of the axially movable tumbler type, to enhance the security of the lock and the ease of key actuation.

Among the objects of the present invention is the provision of a pin tumbler lock assembly having a retaining pin arrangement cooperating with a suitable key. The retaining pins are received in an index ring encompassing the barrel of the lock assembly and extend into the barrel through aligned openings therein. The index ring is stationarily positioned in a lock housing so that the barrel rotates relative thereto when the retaining pins are in their inwardly biased position. A suitable key has actuating surfaces tending to force the pins outwardly partially into the index ring, and depressions in the key surface allow the pins to return to their inoperative position.

Another object of the present invention is the provision of a pin tumbler lock assembly having radial antitorque pins and drivers to additionally preserve the security of the lock. An index ring has a pair of openings aligned with openings in the encompassed barrel to receive inwardly biased antitorque pins and drivers; each pin and driver defining a shear line normally out of alignment with the shear line defined between the index ring and the barrel. A suitable key has a surface engaging the inner ends of the antitorque pins to move them outwardly against the biasing force until the shear lines coincide to allow rotation of the barrel relative to the index ring and lock housmg.

A further object of the present invention is the provision of a pin tumbler lock assembly having a central plug shaft that is rotatable in the lock housing and is actuated by a suitable hollow cylindrically shaped key. The plug shaft at its forward end is provided with a plurality of circumferentially spaced longitudinally extending ribs on the surface thereof, and the hollow key is formed with a like number of longitudinally extending grooves on the interior surface thereof. The grooves in the key receive the ribs on the plug shaft when the key is inserted in the lock and encompasses the shaft end. This cooperation provides proper alignment for the key and a simplified driving connection between the key and shaft which is less prone to tampering.

The present invention also comprehends the provision of a pin tumbler lock assembly having the index ring and retaining pins and a change key to alter the setting of the pin tumblers by rotation to a change position. To provide for removal of the change key in the change position and insertion of a new change key with a'different setting, the index ring is provided with one opening to receive one retaining pin, and the key, on the exterior surface, is provided with a longitudinal slot to allow removal of the key without actuating the opposite retaining pin.

The present invention further comprehends the provision of a pin tumbler lock assembly which may include the index ring with both the retainer pins and the antitorque pins, and the drive connection between the key and plug shaft of the complementary ribs and grooves.

Further objects are to provide a construction of maximum simplicity, efficiency, economy and ease of assembly and operation, and such further objects, advantages and capabilities as will later more fully appear and are inherently possessed thereby.

IN THE DRAWINGS FIG. l is a side elevational view of the withdrawn key and the pin tumbler lock assembly mounted :in a suitable door.

FIG. 2 is a front elevational view of the lock assembly showing the cooperation of the lock bolt with a strike.

FIG. 3 is an exploded perspective view of the lock assembly.

FIG. 4 is a top plan view of the lock assembly and a partial view of the key.

FIG. 5 is an enlarged front elevational view of the lock assembly with portions broken away to show the retaining pins.

FIG. 6 is a vertical cross sectional view taken on the line 6- 6 of FIG. 5.

FIG. 7 is a horizontal cross sectional view taken on the line 7 7 of FIG. 5.

FIG. 8 is a rear elevational view of the lock assembly with the lock bolt, washer and split retainer ring on the shaft.

FIG. 9 is a cross sectional view taken on the line 99 of FIG. 5 with the lock rotated to the change position.

FIG. 10 is a front elevational view of the index ring for the lock assembly.

FIG. I1 is a horizontal cross sectional view taken on the line l ll-lll ofFIG. 110.

FIG. 12 is a front elevational view of an alternate embodiment of index ring.

FIG. 13 is a horizontal cross sectional view taken on the line l313 of FIG. 112.

FIG. 14 is a front elevational view of a second alternate embodiment of index ring.

FIG. 15 is a horizontal cross sectional view taken on the line 15-15 ofFIG. 114.

FIG. 16 is a side elevational view of a pass key for the lock assembly.

FIG. 17 is an end elevational view of the key of FIG. 16.

FIG. 18 is a side elevational view of the key of FIG. 16 partially broken away to show the retaining pin depressions.

FIG. 19 is a side elevational view, partially broken away, showing a change key for the lock.

FIG. 20 is an end elevational view of the key of FIG. 19.

Referring more particularly to the disclosure in the drawings wherein is shown an illustrative embodiment of the present invention, FIG. 1 discloses a pin tumbler lock as sembly 10 for the actuation of a suitable lock bolt 11 or other locking mechanism, the lock assembly being inserted in an opening adjacent the edge of a door 12 and retained therein by a nut 13 threadingly engaging the threaded exterior surface 14 of a lock cylinder 15. The lock cylinder 15 includes a generally cylindrical body having oppositely disposed flattened portions 16,16 to be received in a complementary opening to prevent rotation of the cylinder 15 relative to the door 12, and an enlarged flange 17 providing a face 18 for the lock assembly and a shoulder 19 engaging the exterior surface of the door 12. The lock bolt 11 cooperates or engages with a suitable strike member 20.

The lock cylinder I5 is provided with :a generally cylindrical passage 21 therethrough counterbored at 22 within the flange 17 and further counterbored at 23 at the face 18 of the cylinder. A pair of diametrically opposed longitudinally extending grooves or slots 24,24 are formed in the passage 21 with the maximum distance between the bottom surfaces of the slots being less than the diameter of the counterbore 22. The flange 17 is provided on its exterior generally conical surface with an indexing mark 25 indicating the vertical position for the cylinder and a pair of spaced secondary indices 26,26, one of which indicates the change position for the lock. At the opposite end, a lug 27 extending for a suitable arc of travel around the cylinder aids in limiting rotary movement of the lock bolt 11.

Within the lock cylinder 15 are located a rear cylindrical barrel 28, a center generally cylindrical barrel 29 having a pair of diametrically opposed longitudinally extending ribs 30,30 received in the grooves 24,24 of the lock cylinder 15, and a cylindrical front barrel 3] having a slight enlargement 32 and an end flange 33 received in the counterbore 23. A plug shaft 34 extends through central openings 35 in the barrels 28, 29

and 31 and terminates at the forward end in a plug nose 36 in a cylindrical chamber 37 in the barrel 31, the nose having a smooth cylindrical surface with three longitudinally extending and circumferentially equally spaced ribs 39 extending from the rear wall 38 of the chamber to an inclined surface 40 terminating the rib approximately one-half the distance from the wall 38 to the conical end 41 of the nose.

The plug shaft 34 extends rearwardly from the rear barrel 28 and the rear end of the lock cylinder 15 providing a cylindrical surface 42 (FIG. 8) with opposed flattened sides 43,43 and a generally annular groove 44 intersects the sides 43,43 at a point spaced from the rear end of the shaft. A stop washer 45 having a central opening complementary to the cylindrical surface 42 and flattened sides 43,43 is mounted on the shaft abutting the end of the cylinder 15, the lock bolt 11 also having an opening conformably receiving the shaft abuts the washer, and a spring retainer ring 46 or other suitable means engages in the groove 44 to retain the lock bolt 11 and stop washer 45 on the shaft. A washer 47 is located on the plug shaft 34 abutting a shoulder on the plug nose 36 and received in a recess 48 (FIG. 6) in the front barrel 31.

The stop washer 45 may have any suitable peripheral configuration, such as lugs 48a, to cooperate with the arcuate projection or lug 27 to limit the arc of travel of the lock bolt 11 to 90 or 180", or the washer may not have a lug to allow a 360 rotation of the lock bolt. The front barrel 31 and the rear barrel 28 are secured to the plug shaft 34 by pins 49 and 50, respectively, extending diametrically through openings 51, the

shaft 34 and projecting into openings 51a in the barrels 28 and 31; the pins being frictionally retained in the shaft and barrels. Thus, the shaft 34 and front and rear barrels 31 and 28, respectively, rotate simultaneously while the center barrel 29 is stationary in the lock cylinder 15.

As previously known from the Monahan U.S. Pat. No. 3,422,646, the front barrel 31 and rear barrel 28 are provided with a plurality of aligned circumferentially equally spaced and axially extending passages 52,53, shown as six in number. The center barrel 29 has twice as many circumferentially equally spaced axially extending passages 54, 54a. With the lock assembly in locked position and the key inserted, the passages 52 in the front barrel 31 each contains a tumbler 55, the aligned passages 54 in the center barrel 29 contain the locking pins 56, the alternate passages 54a in the center barrel contain the change tumblers 57, and the passages 53 in the rear barrel 28 contain change tumblers 57 and tumbler springs 58.

With the proper key inserted, the shear lines 59, 59 between the three barrels are aligned with the shear lines defined by the tumblers 55, locking pins 56 and change tumblers 57, while with the key retracted the locking pins 56 extend over one of the two shear lines 59 to prevent rotary movement. The plurality of change tumblers 57 are provided so that when the lock is moved to the change position to be later described, the arrangement of the change tumblers in the passages 52 and 53 can be altered.

Located within the chamber defined by the counterbore 22 is an index ring 61 encompassing the forward end of the front barrel 31; the index ring having a generally annular configuration with an annular groove 62 in the outer surface and a pair of oppositely disposed rearwardly extending ribs 63,63 which extend into the grooves 24,24 in the lock cylinder so that the ring is stationary in the lock cylinder. The index ring 61 has a cylindrical passage which is counterbored to provide a shoulder 64 cooperating with the shoulder formed on the enlargement 32 of the front barrel 31 and spacing the index ring from the flange 33.

At the front edge of the index ring 61 (FIGS. 3, 10 and 11) are a pair of diametrically opposed notches 65, 65 and a pair of secondary notches 66,66 are formed on the opposite sides of and spaced from the upper notch 65. A pair of diametrically opposed stepped openings 67,67 are formed in the front barrel 3] normally generally aligned with the opposed notches 65,65 to receive a pair of retaining pins 68,68 therein. A resilient O- ring 69 is positioned (FIG. 6) in the space between the index ring 61 and the flange 33 and engages the outer ends of the retaining pins 68. Each pin 68 has a reduced diameter inner shank portion 71 in the stepped opening with a rounded end 72 projecting into the chamber 37 to engage a suitable key to be later described.

Rearwardly of the notches 65,65,66,66 is located the groove 62 receiving a second resilient O-ring 73. Aligned with the groove 62 are a second pair of radial openings 74,74 which are normally aligned with stepped radial openings 75,75 in the front barrel 31. No more than one of the radial openings 74 is longitudinally aligned with a notch 65. Therefore, as shown in FIGS. 6, 10 and 11, the radial openings 74,74 and 75,75 are spaced from each other at an angle of I20". As seen in FIG. 10, the upper notch 65 and upper radial opening 74 are longitudinally aligned at a 12 oclock position and the second opening 74 is at a 4 oclock position.

The radial openings 74,74 (FIG. 6) each receive a driver 76 engaging the resilient O-ring 73 extending across and into the openings. Each stepped opening 75 receives an antitorque pin 77 having a reduced diameter inner end 78 projecting into the chamber 37 to engage the exterior surface of a proper key 79 (FIG. 16). When the proper key is inserted into the lock, the exterior surface 83 of the key 79 will engage the rounded ends 78,78 of the antitorque pins 77,77 and urge the pins 77,77 and drivers 76,76 outwardly against the force of the O-ring 73 to align the shear line defined by the line of contact between each driver and antitorque pin with the shear line defined between the index ring 61 and the front barrel 31 so that the antitorque pins or drivers will not interfere with rotation of the front barrel 31 and the plug nose 36 and shaft 34 relative to the index ring 61 and the lock cylinder 15.

As seen in FIGS. 12, 13, 14 and 15, the openings in the index ring 61 for the antitorque pins can be arranged in numerous locations, as well as others not shown. In FIGS. 12 and 13, the radial openings 74a, 74a for the index ring 610 are arranged at the 2 oclock and 10 oclock positions. The notches 65a,65a and secondary notches 66a, 66a remain at the positions shown in FIGS. 5, 6, 10 and 11. In FIGS. 14 and 15, the index ring 61b has identically positioned notches 65b,65b and secondary notches 66b,66b, but the radial openings 74b,74b are located at the 2 oclock and 4 oclock positions. Obviously, the radial openings 75,75 in the front barrel 31 would be suitably aligned with the openings 74a,74a or 74b,74b. Other possible positions of the openings 74,74 include the combinations of (l) 12 o'clock and 8 oclock, (2) 4 oclock and 8 oclock, (3 12 oclock and 2 oclock, (4) 12 oclock and 10 oclock, (5) 8 oclock and 10 o'clock, (6) 2 oclock and 8 o'clock, and (7) 4 oclock and I0 oclock.

Now considering the key 79 (FIGS. 16, 17 and 18) utilized for actuation of the lock, the key includes a flat key bow 81 of any suitable periphery for ease of handling and a hollow key barrel 82 which is generally cylindrical with an exterior surface 83 and an interior generally cylindrical surface 84 interrupted by three circumferentially equally spaced longitudinally extending grooves 85 extending the length of the barrel. The bow 81 is secured to the barrel by inserting the bow through a diametrically extending slot 86 and a pin or rivet 87 extends through aligned openings in the barrel 82 and the bow 81 and suitably secured therein. At the forward end of the key barrel are provided suitable key bittings 88 which engage and cooperate with the lock tumblers 55 to actuate the tumblers so that the plug shaft 34, the plug nose 36, the front barrel 31, the rear barrel 28, and the lock bolt 11 can rotate relative to the lock cylinder 15.

The exterior surface 83 of the barrel 82 has a pair of oppositely disposed depressions 89,89 which are adapted to be aligned with the rounded ends 72 of the retaining pins 68 so that the resilient O-ring 69 will urge the retaining pins 68 inwardly to solely reside in the front barrel 31 and not obstruct rotation of the front barrel 31 relative to the index ring 61. If the depressions 89,89 are not present or are not of the proper depth, the retaining pins 68 will be moved into the notches 65,65 in the index ring to prevent rotation of the front barrel 31 and associated structure. Once the proper key has been inserted and rotated so the retaining pins 68 are no longer aligned with the notches 65,65, the engagement of the retaining pins 68 in the depressions 89,89 prevents removal of the key; the inner surface of the counterbored passage in the index ring 61 preventing any outward movement of the retaining pins 68. Also, the surface 83 may have any suitable configuration aligned with and actuating the antitorque pins 77 and drivers 76 to allow rotation of the barrel 31.

FIGS. 19 and 28 disclose a set or change key 91 having a key bow 92 secured to a hollow cylindrical key barrel 93 by a pin 94 passing diametrically therethrough. The barrel 93 has internal longitudinally extending grooves 95 and the external key bittings 96 and one retaining pin depression 97 shown at the top of the barrel 93 in FIG. 19. However, instead of the opposite depression, the barrel is provided with a slot or groove 98 of the same depth as the depression 97 and extending from the bitted end 99 of the barrel to a point aligned with the depression 97. Thus, when the key 91 is rotated to the change position shown in FIG. 9, the upper retaining pin 68 is aligned with one of the secondary notches 66 in the index ring 61, and the lower pin 68 is in the groove 98. The key 91 can then be withdrawn and a change key with a different bitting inserted and rotated to normal position.

In operation with the lock assembly in normal locked position, a proper key 79 is inserted into the chamber 37 surrounding the plug nose 36 with the bittings 88 engaging the tumblers 55 and forcing them rearwardly against the force of the springs 58, and the exterior surface 83 of the key barrel 82 engages the ends 72 of the retaining pins 68 to force them outward against the force of the O-ring 69 into the opposed notches 65,65, and engage the ends of the antitorque pins 77 and force these pins 77 and drivers 76 outward against the force of the second O-ring 73 in the groove 62.

As the key enters, the longitudinal ribs 39 on the plug nose 36 enter the complementary grooves 85 in the key barrel 82 so the key and plug nose will rotate together, When the key 79 has reached a position abutting the rear wall 38 of the chamber 37, the retaining pins 68,68 are aligned with and biased into the depressions 89,89 in the key barrel so that the retaining pins 68 are solely within the openings 67,67 in the barrel 31, the shear line of the antitorque pins 77 and drivers 76 is aligned with the shear line of the index ring 61 and barrel 31, and the shear lines of the locking pins 56, tumblers 55 and change tumblers 57 are aligned with the shear lines 59 of the center barrel so that the key 79, plug nose 36, plug shaft 34', front barrel 31, rear barrel 28, the stop washer 65, and the lock bolt 11 can rotate within the limits imposed by the washer 45 and the projection 27 on the lock cylinder to move the bolt between locked and unlocked positions. Because of the retaining pins 68,68 in the depressions 89,89, the key 79 cannot be removed until the lock is returned to its original locked position.

To change the arrangement of the change tumblers 57 relative to the tumblers 55 and the locking pins 56, a change key 91 is utilized. Starting with the lock assembly 10 in its locked position, the change key 91 having the proper bittings for the lock is inserted into the chamber 37 and actuates the retaining pins 68, the antitorque pins 77 and drivers 76 and the tumblers 55 in the manner previously described, except the lower retaining pin 68 is not moved because of the longitudinal groove 98 on the exterior surface of the key barrel 93. Once the key is fully inserted and the grooves 95 in the key barrel 93 engage the ribs 38, the key 91 is rotated counterclockwise through an arc of 30 so that the bow 92 is aligned with a secondary index mark 26. At this point, the upper retaining pin 68 is aligned with a secondary notch 66 in the index ring 61, and the passages 52 and 53 in the front barrel 31 and the rear barrel 28, respectively, are aligned with the alternate passages 54a in the center barrel 29 providing a line of change tumblers 57 as seen in FIG. 9. The key 91 is then removed as allowed by the secondary notch 66 and the slot 98 in the key barrel 93 with the tumbler springs 58 forcing the tumblers 55 and change tumblers 57 forwardly.

A new key 91 having different key bittings 96 is then inserted into the lock 10 in the change position to reset the tumblers 55 and change tumblers 57 in a new arrangement, as more clearly disclosed in the Monahan U.S. Pat. No. 3,422,646, and the key is rotated to the locked position where the key bow 92 is aligned with the primary index mark 25, and the key is removed. Then a new key 79 having bittings 88 identical to those of the new change key 91 maybe used to ac tuate the lock and rotate the lock bolt 11 between locked and unlocked positions as seen in FIG. 2.

The use of the pass key and change key and their cooperation with the plug nose through the grooves and ribs is generally limited to an axial pin tumbler lock; however, the use of the index ring with the retaining pins or the antitorque pin or both is not limited to the lock shown, but can be utilized with the rotary plug for a pin tumbler or plate tumbler lock with suitable modifications of the key. While the improvements have been shown and described as being advantageously applicable to an axial pin tumbler lock, it is not out desire or intent to unnecessarily limit the scope or the utility of the improved features by virtue of this illustrative embodiment.

Having thus disclosed our invention, we claim:

1. A lock comprising a lock cylinder having a passage therethrough, a rotatable plug assembly received in said passage and having a key receiving space therein, an index ring located in said lock cylinder encompassing said plug assembly, means securing said index ring in said lock cylinder, said index ring having at least two radial openings therein, said plug assembly having a like number of openings therein normally aligned with the openings in said index ring, a pin received in each of said openings in the plug assembly and projecting into said key receiving space, and means biasing said pins inwardly so as to engage the exterior surface of a proper key and allow rotation of said plug assembly relative to said index ring and lock cylinder.

2. A lock as set forth in claim 1, in which said openings comprise a plurality of circumferentially spaced notches formed on the front edge of said index ring, and said pins are stepped retaining pins normally received in stepped openings in said plug assembly, such that the exterior surface of an improper key will force the retaining pins partially outwardly into said notches to block rotation of said plug assembly.

3. A lock as set forth in claim 2, in which said biasing means includes a resilient ring encompassing said plug assembly adjacent said notches and engaging the outer ends of said retainmg pins.

4. A lock as set forth in claim 2, in which a proper key has an external surface with depressions aligned with and receiving the inner ends of said retaining pins so that the retaining pins solely reside in said plug assembly to allow rotation thereof.

5. A lock as set forth in claim 1, in which said securing means includes a pair of rearwardly extending projections on said index ring, said lock cylinder having a pair of longitudinally extending grooves in said passage receiving said projections.

6. A lock as set forth in claim 1, in which said openings are spaced around and extend radially through said index ring, said index ring having an annular groove on the exterior surface thereof intersecting said radial openings, and said pins include sets of antitorque pins and drivers therefor received in the aligned radial openings in said plug assembly and said index ring, said antitorque pins projecting into said key receiving space with said pins and drivers normally intersecting the shear line defined between said index ring and said plug assembly.

7. A lock as set forth in claim 6, in which said biasing means includes a resilient ring received in said annular groove and engaging said drivers, such that the external surface of a proper key engages the inner ends of said antitorque pins and positions said antitorque pins and drivers so that their meeting line coincides with the shear line between the index ring and the plug assembly to allow rotation of the key and plug assembly.

8. A lock as set forth in claim 3, in which at least two radial openings are formed in said index ring on a circumference spaced rearwardly of said notches, said index ring having an annular groove on the exterior surface intersecting said openings, a resilient ring in said groove, said plug assembly having radial openings normally aligned with said last mentioned radial openings, each aligned pair of radial openings receiving an antitorque pin and a driver, said resilient ring engaging the outer ends of said drivers, the inner ends of said an- 10. A lock as set forth in claim 1, in which said openings in I said index ring comprise a pair of oppositely disposed notches at the front edge of said index ring and a pair of spaced radial openings on a circumference spaced rearwardly of said notches, said index ring having an annular groove on the exterior surface intersecting said radial openings, a first resilient O-ring encompassing said plug assembly adjacent said notches, and a second resilient O-ring received in said annular groove, said plug assembly having radial openings normally aligned with said opposed notches and said radial openings in said index ring, a pair of retaining pins received in said openings in the plug assembly aligned with said notches and engaging said first resilient O-ring and a pair of antitorque pins and drivers in said aligned radial openings in said index ring and plug assembly, the inner ends of said retaining pins and antitorque pins projecting into said key receiving space to engage an exterior surface of a proper key.

11. A lock as set forth in claim 10, in which no more than one of said antitorque pins is longitudinally aligned with said retaining pins.

12. A lock as set forth in claim 10, in which none of said antitorque pins is longitudinally aligned with said retaining pins.

13. A lock as set forth in claim 10, in which a key has an exterior surface engaging said antitorque pins to align the meeting lines of the antitorque pins and drivers with the shear line between said index ring and plug assembly, said exterior surface having a pair of diametrically opposed depressions receiving the inner ends of said retaining pins to allow the retaining pins to be retracted within said plug assembly.

14. A lock as set forth in claim 10, including axial pin tumblers, said plug assembly being shiftable between a locked position and a tumbler changing position, said index ring having at least one secondary notch spaced from one of said opposed notches and 'aligned with a radial opening in said plug assembly in the tumbler changing position, and said proper key has an exterior surface with a depression and an oppositely disposed longitudinally extending slot receiving said retaining pins.

15. A lock as set forth in claim 1, in which said plug assembly includes a generally cylindrical plug nose extending into said key receiving space, a plurality of circumferentially spaced longitudinally extending ribs formed on said plug nose, and a proper key adapted to enter said key receiving space and provided with a hollow key barrel encompassing said plug nose and having longitudinally extending grooves on the interior surface thereof receiving said ribs.

16. A key for a tumbler lock having a rotatable barrel and a cylindrical plug nose defining an annular key receiving space therebetween, comprising a hollow cylindrical key shank adapted to enter the annular key receiving space and encompass said plug nose, said shank having a flat unbroken peripheral edge at the forward end thereof with blttlngs formed on the exterior surface of the shank adapted to cooperate with the tumblers of the tumbler lock, and a generally cylindrical interior surface with a plurality of circumferentially spaced longitudinally extending grooves therein extending to the forward edge of the shank, and said plug nose has a like number of longitudinally extending ribs thereon aligned with and received in said grooves so that the key and plug nose cooperate to rotate simultaneously, each rib having an inclined forward end surface merging into the plug nose short of the outer end thereof.

17. A key as set forth in claim 16, in which said shank has one or more depressions formed in the cylindrical exterior surface thereof adapted to receive the inner ends of a comparable number of radial pins in said rotatable barrel.

18. A key for a tumbler lock having a rotatable barrel and a plug nose defining a key receiving space therebetween, comprising a hollow cylindrical key shank adapted to enter said key receiving space and encompass said plug nose, said shank having a generally cylindrical interior surface with a plurality of circumferentially spaced longitudinal grooves therein extending therethrough, and said plug nose has a like number of longitudinally extending ribs aligned with and received in said grooves so that the key and plug nose cooperate to rotate simultaneously, said key shank having a depression in the exterior surface of the shank and a longitudinal slot in the exterior surface diametrically opposite said depression and extending from the open end of the shank to a point transversely aligned with said depression, said depression and slot receiving a pair of oppositely disposed pins in said barrel.

19. A key as set forth in claim 18, in which said barrel and plug nose of the tumbler lock are shiftable between a locked position and a tumbler change position, and said slot allows removal of said key from said tumbler lock in the tumbler change position. 

1. A lock comprising a lock cylinder having a passage therethrough, a rotatable plug assembly received in said passage and having a key receiving space therein, an index ring located in said lock cylinder encompassing said plug assembly, means securing said index ring in said lock cylinder, said index ring having at least two radial openings therein, said plug assembly having a like number of openings therein normally aligned with the openings in said index ring, a pin received in each of said openings in the plug assembly and projecting into said key receiving space, and means biasing said pins inwardly so as to engage the exterior surface of a proper key and allow rotation of said plug assembly relative to said index ring and lock cylinder.
 2. A lock as set forth in claim 1, in which said openings comprise a plurality of circumferentially spaced notches formed on the front edge of said index ring, and said pins are stepped retaining pins normally received in stepped openings in said plug assembly, such that the exterior surface of an improper key will force the retaining pins partially outwardly into said notches to block rotation of said plug assembly.
 3. A lock as set forth in claim 2, in which said biasing means includes a resilient ring encompassing said plug assembly adjacent said notches and engaging the outer ends of said retaining pins.
 4. A lock as set forth in claim 2, in which a proper key has an external surface with depressions aligned with and receiving the inner ends of said retaining pins so that the retaining pins solely reside in said plug assembly to allow rotation thereof.
 5. A lock as set forth in claim 1, in which said securing means includes a pair of rearwardly extending projections on said index ring, said lock cylinder having a pair of longitudinally extending grooves in said passage receiving said projections.
 6. A lock as set forth in claim 1, in which said openings are spaced around and extend radially through said index ring, said index ring having an annular groove on the exterior surface thereof intersecting said radial openings, and said pins include sets of anti-torque pins and drivers therefor received in the aligned radial openings in said plug assembly and said index ring, said anti-torque pins projecting into said key receiving space with said pins and drivers normally intersecting the shear line defined between said index ring and said plug assembly.
 7. A lock as set forth in claim 6, in which said biasing means includes a resilient ring received in said annular groove and engaging said drivers, such that the external surface of a proper key engages the inner ends of said anti-torque pins and positions said anti-torque pins and drivers so that their meeting line coincides with the shear line between the index ring and the plug assembly to allow rotation of the key and plug assembly.
 8. A lock as set forth in claim 3, in which at least two radial openings are formed in said index ring on a circumference spaced rearwardly of said notches, said index ring having an annUlar groove on the exterior surface intersecting said openings, a resilient ring in said groove, said plug assembly having radial openings normally aligned with said last mentioned radial openings, each aligned pair of radial openings receiving an anti-torque pin and a driver, said resilient ring engaging the outer ends of said drivers, the inner ends of said anti-torque pins projecting through said plug assembly into said key receiving space.
 9. A lock as set forth in claim 8, in which no more than one of said anti-torque pins is longitudinally aligned with said retaining pins.
 10. A lock as set forth in claim 1, in which said openings in said index ring comprise a pair of oppositely disposed notches at the front edge of said index ring and a pair of spaced radial openings on a circumference spaced rearwardly of said notches, said index ring having an annular groove on the exterior surface intersecting said radial openings, a first resilient O-ring encompassing said plug assembly adjacent said notches, and a second resilient O-ring received in said annular groove, said plug assembly having radial openings normally aligned with said opposed notches and said radial openings in said index ring, a pair of retaining pins received in said openings in the plug assembly aligned with said notches and engaging said first resilient O-ring and a pair of anti-torque pins and drivers in said aligned radial openings in said index ring and plug assembly, the inner ends of said retaining pins and anti-torque pins projecting into said key receiving space to engage an exterior surface of a proper key.
 11. A lock as set forth in claim 10, in which no more than one of said anti-torque pins is longitudinally aligned with said retaining pins.
 12. A lock as set forth in claim 10, in which none of said anti-torque pins is longitudinally aligned with said retaining pins.
 13. A lock as set forth in claim 10, in which a key has an exterior surface engaging said anti-torque pins to align the meeting lines of the anti-torque pins and drivers with the shear line between said index ring and plug assembly, said exterior surface having a pair of diametrically opposed depressions receiving the inner ends of said retaining pins to allow the retaining pins to be retracted within said plug assembly.
 14. A lock as set forth in claim 10, including axial pin tumblers, said plug assembly being shiftable between a locked position and a tumbler changing position, said index ring having at least one secondary notch spaced from one of said opposed notches and aligned with a radial opening in said plug assembly in the tumbler changing position, and said proper key has an exterior surface with a depression and an oppositely disposed longitudinally extending slot receiving said retaining pins.
 15. A lock as set forth in claim 1, in which said plug assembly includes a generally cylindrical plug nose extending into said key receiving space, a plurality of circumferentially spaced longitudinally extending ribs formed on said plug nose, and a proper key adapted to enter said key receiving space and provided with a hollow key barrel encompassing said plug nose and having longitudinally extending grooves on the interior surface thereof receiving said ribs.
 16. A key for a tumbler lock having a rotatable barrel and a cylindrical plug nose defining an annular key receiving space therebetween, comprising a hollow cylindrical key shank adapted to enter the annular key receiving space and encompass said plug nose, said shank having a flat unbroken peripheral edge at the forward end thereof with bittings formed on the exterior surface of the shank adapted to cooperate with the tumblers of the tumbler lock, and a generally cylindrical interior surface with a plurality of circumferentially spaced longitudinally extending grooves therein extending to the forward edge of the shank, and said plug nose has a like number of longitudinally extending ribs thereon aligned with and received in said grooves sO that the key and plug nose cooperate to rotate simultaneously, each rib having an inclined forward end surface merging into the plug nose short of the outer end thereof.
 17. A key as set forth in claim 16, in which said shank has one or more depressions formed in the cylindrical exterior surface thereof adapted to receive the inner ends of a comparable number of radial pins in said rotatable barrel.
 18. A key for a tumbler lock having a rotatable barrel and a plug nose defining a key receiving space therebetween, comprising a hollow cylindrical key shank adapted to enter said key receiving space and encompass said plug nose, said shank having a generally cylindrical interior surface with a plurality of circumferentially spaced longitudinal grooves therein extending therethrough, and said plug nose has a like number of longitudinally extending ribs aligned with and received in said grooves so that the key and plug nose cooperate to rotate simultaneously, said key shank having a depression in the exterior surface of the shank and a longitudinal slot in the exterior surface diametrically opposite said depression and extending from the open end of the shank to a point transversely aligned with said depression, said depression and slot receiving a pair of oppositely disposed pins in said barrel.
 19. A key as set forth in claim 18, in which said barrel and plug nose of the tumbler lock are shiftable between a locked position and a tumbler change position, and said slot allows removal of said key from said tumbler lock in the tumbler change position. 